MSI HD R7770 Power Edition Review @ OCC
 

Overclocking was a very simple process. AMD Overdrive was too limited on speed options so I quickly switched over to MSI Afterburner. Unfortunately the Triple-Overvoltage features would not enable for me. With default voltages the card was fully stable at 1183MHz core and 1450MHz memory with 20% increased Power Limit. Any more than that on the core would be unstable in different benchmarks while memory could go further. These speeds are amazing considering the full potential of the card hasn't been utilized yet. Temperatures were great too and the core could possibly run a little cooler by replacing the thermal paste.

http://www.overclockersclub.com/reviews/msi_7770_pe/